This application is related to co-pending application Ser. No. 321,224 filed on Nov. 13, 1981.
This invention relates generally to radar systems for vehicles, and more particularly, the present invention relates to apparatus and method for detecting obstacles in the path of a moving vehicle, for example, behind a backing automobile by using an ultrasonic detector.
Various systems for detecting the presence of obstacles behind a backing vehicle are known. Conventional alarming devices for such use employs an ultrasonic radar system. Namely, ultrasonic wave pulses are transmitted backward when a motor vehicle is backing so that waves or echos reflected at obstacles are received. The received echo signal is processed to detect the presence of obstacles or to detect the distance between the motor vehicle and the obstacle. When an obstacle is detected to be close to the motor, an alarm is given to the vehile driver so that he or she can stop the backing vehicle to prevent undesirable collision. However, in such conventional detecting and alarming systems, the detecting circuit therein is apt to malfunction due to echos reflected at obstacles which are located far from the vehicle. For instance, if there is a wall, fence or the like at a distance relatively far from a backing vehicle, a false detection signal is apt to be produced, which undesirably alerts the vehicle driver. The production of such a false detection signal is caused by repetitive transmission of ultrasonic wave pulses which is necessary to continuously detect obstacles during the backward movement of the vehicle. Namely, an echo signal caused by ultrasonic wave pulse transmitted in a former cycle is apt to be received in a subsequent cycle when the obstacle is located far behind the vehicle. Since such an echo signal is processed as an echo signal corresponding to the ultrasonic wave pulse transmitted in the present cycle, it has been inevitable to distinguish an echo signal from a far obstacle from another echo signal from a close obstacle.